Internal combustion engines used to operate motor vehicles or heavy mechanical equipment generate considerable heat that must be dissipated. If not properly dissipated, heat reduces operating efficiency of the engine and can ultimately lead to damage of the engine.
Engine cooling systems typically flow a cooling fluid through the block of the engine to cool the engine. The cooling fluid captures heat from the engine and releases the heat through a heat exchanger in which the cooling fluid passes in heat exchange relationship with air or liquid. An air-to-liquid heat exchanger may include a series of tubes through which the cooling fluid is pumped, and airflow induced by a fan cools the tubes, and hence the cooling fluid flowing through the tubes. The cooling fluid can be pumped through various engine components, such as the engine head and block, an engine oil cooler or the like, to remove heat from the various engine components.
In the operation of an internal combustion engine, the amount of combustion air that can be delivered to the intake manifold of the engine, for combustion in the engine cylinders, is a limiting factor in the performance of the engine. Atmospheric pressure is often inadequate to supply the required amount of air for proper and efficient operation of an engine.
Thus, an engine may include one or more turbochargers for compressing air to be supplied to one or more combustion chambers within corresponding combustion cylinders. The turbocharger supplies combustion air at a higher pressure and higher density than existing atmospheric pressure and ambient density. The use of a turbocharger can compensate for lack of power due to altitude, or to increase the power that can be obtained from an engine of a given displacement, thereby reducing the cost, weight and size of an engine required for a given power output. The turbocharger typically includes a turbine driven by exhaust gases from the engine, and one or more compressors driven by the turbine through a turbocharger shaft common to both the turbine and the compressor or compressors. A stream of exhaust gases from the engine is conducted from the exhaust manifold to the turbine, and the exhaust gas stream passing through the turbine causes a turbine wheel to rotate. Rotation of the turbine wheel rotates the common shaft interconnecting the turbine wheel and one or more compressor wheels in the compressor section, thereby rotating the compressor wheels. Air to be compressed is received in the compressor section, wherein the air is compressed and supplied to the air intake system of the engine.
The boost air flowing from the compressor or compressors may be conditioned to affect the overall turbocharger performance and/or the engine efficiency. In turbochargers having multiple stage compressors, compressing the air in the first compressor significantly raises the temperature of the air, increasing the power required by the second compressor to achieve a desired pressure boost. To overcome the detrimental effects of the increase in temperature, so called “intercoolers” have been provided in the flow path between the first compressor outlet and the second compressor inlet. Similarly, so called “aftercoolers” have been used after the turbocharger in turbochargers having both single stage and multi-stage compressors. The aftercooler cools the compressed air being supplied to the intake manifold, thereby increasing the oxygen content per unit volume, to better support combustion in the cylinders and decrease engine operating temperatures.
Certain cooling systems use cooling fluid from the engine cooling system to circulate through the aftercooler, providing a heat exchange medium for the compressed air also flowing through the aftercooler. Heat from the compressed air stream is removed by the cooling fluid and absorbed in the heat exchanger. Reducing the temperature of the charge air can reduce engine emissions and increase engine efficiency.
An aftercooler system may also provide a separate cooling fluid circuit from the heat exchanger to the aftercooler, including a separate circuit aftercooler (SCAC) pump for circulating the cooling fluid to the aftercooler. However, the cooling efficiency of such systems has not always met expectations under all operating conditions.
U.S. Pat. No. 6,609,484 describes a cooling system for an internal combustion engine, with a radiator assembly including a first group of radiator cores and a second group of radiator cores. Some cooling fluid cooled in the first group of radiator cores is passed from the radiator assembly to an engine cooling circuit. Another portion of cooling fluid cooled in the first group of radiator cores is passed to the second group of radiator cores, for additional cooling thereof. From the second group of radiator cores, cooling fluid is passed to the separate circuit aftercooler cooling circuit. A turbocharged engine cooling system using a two-pass heat exchanger and a separate circuit aftercooler pump in an aftercooler cooling circuit is also shown in U.S. Pat. No. 6,158,399.
In view of the engine efficiency and emissions reduction benefits obtained from adequate aftercooling of the combustion air, it is desirable to have an improved cooling system that provides adequate aftercooler cooling while maintaining sufficient cooling of various other engine components under various operating conditions.
The present disclosure is directed to addressing one or more needs as set forth above.